Aquaculture and human health

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1 Aquaculture and human health Jimmy Turnbull Institute of Aquaculture University of Stirling Scotland UK 1

2 Introduction zoonosis The transmission of a disease from an animal or nonhuman species to humans. The natural reservoir is a nonhuman animal. This excludes infections where humans are part of the natural life cycle 2

3 Introduction True aquatic zoonosis relatively rare Restricted to specific human populations This lecture will cover: All human health issues associated with aquaculture 3

4 Introduction 1. Hazards of new aquatic habitats 2. Hazards from eating aquatic products 3. True zoonosis 4

5 1. New Aquatic habitats 5

6 New Aquatic habitats Increased availability of water Drinking, washing, fishing, recreation Increased contact between people and pathogens or vectors 6

7 New Aquatic habitats Feeding or fertilisation increases organic load = Eutrophication Multiplication of vectors Survival of pathogens 7

8 Multiplication of vectors Breeding site for terrestrial vectors Mosquitoes Malaria and others Tabanid flies - Trypanosomiasis or Sleeping sickness. Rats -Leptospira spp. Breeding site for aquatic vectors Snails 8

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10 For example Cercarial dermatitis or Swimmers itch Schistosomiasis or Belharzia (one form of swimmers itch) 10

11 Falariasis or Elaphantiasis Wuchereria bancrofti, Brugia malayi and B. timori 11

12 Onchocerciasis or River blindness 12

13 Onchocerciasis or River blindness 13

14 Malaria Plasmodium spp. 400 to 500 million cases per year >1 million deaths per year Mostly children in sub-saharan Africa 14

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16 Survival of pathogens e.g. Cholera Vibrio cholerae 16

17 2. Hazards from eating aquatic products Not true zoonoses 17

18 Hazards from eating aquatic products Most result from contamination of food with toxin producing or food poisoning organisms Usually associated with poor handling or storage More problems with warm blooded animals Less of a problems with aquatic products because they rot quickly 18

19 Hazards from eating aquatic products Infectious contaminants e.g. Hepatitis A shellfish Cholera - shellfish Contamination with biological toxins Clostridium botulinum - botulism Organically rich material with low O 2 Associated with processed fish 19

20 Hazards from eating aquatic products Contamination with biological toxins Shell fish poisoning Amnesic, diarrhoeic, paralytic ASP DSP PSP 20

21 Hazards from eating aquatic products Contamination with biological toxins Scromboid toxin Puffer fish fugu tetrodontotoxin 21

22 Hazards from eating aquatic products Non-infectious contaminants Pollutants Heavy metals Herbicides Pesticides Others Chemotherapeutants 22

23 Parasites of fish and humans Diphylobothrium latum Broad tape worm of man Adult lives in the gut of a mammal e.g. man Adult can be over 3m Can live for years Cause chronic debilitation and pernicious anaemia in man 23

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27 Parasites of fish and humans Diphylobothrium latum Widespread in North Europe, Russia, Africa, North and South America, Asia. Prevalence in humans up to 25% Control : Don t eat Raw, pickled, poorly cooked fish. Frozen/hot smoked/cooked/brined - OK 27

28 3. True zoonosis 28

29 Very low incidence Bacterial zoonosis Different bacterial flora or at least strains e.g. Vibrio parahaemolyticus disease in humans and aquatic animals Temperature - psychrophilic Superficial tissues - Mycobacterium spp. Immuno-suppressed e.g. AIDS Aeromonas hydrophila 29

30 In fish Mycobacteriosis 3 species - may be more Chronic condition, fresh water and marine species Multiple internal granulomas and low persistent mortalities Difficult to culture In humans All 3 species cause lesions, M.marinum most common Restricted to superficial infections Known as aquarist nodule or swimming pool granuloma 30

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32 Mycobacteriosis People working with infected fish or water Entry through open wounds Treatment in humans can be problematic and require protracted chemotherapy Surgery may result in the spread of the infection down lymphatics 32

33 Mycobacteriosis Control in fish based on exclusion of the infection and destruction of infected stocks Not easy hence the widespread distribution in food and ornamental species Drugs not used due to : Cost Resistance 33

34 Trematoda digenean flukes Eggs of parasites lodge in heart and brain Flukes grow in liver Chinese liver fluke Flukes lodge in larynx - Clinostomum complanatum Causes mortalities in populations eating fermented fish in SE Asia Prevalence of > 95% in some populations Control - Don t eat raw or fermented fish 34

35 Digenean flukes Heterophydae Life cycle Or Egg Metacercaria Cercaria Miricidium Sporocyst 35

36 Nematods Anasakis spp. Herring worm - occurs in range of species of fish Mostly in oily fish, herring and mackerel Normal final host sperm whale White worm <15mm Occurs in the muscle of fish or migrates to the muscle after the fish killed Rapid gutting will remove 50% 36

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38 Anasakis spp. Most reported in Japan & Netherlands In humans - vomiting and pain 4 to 6 hours after eating infected material If untreated they may result in chronic lower abdominal pain, difficult to diagnose May cause fatal anaphylaxis or penetration of the worms into the abdomen can result in fatal acute abdominal syndrome 38

39 Other Nematodes Gnathostoma spp. Under the skin = Creeping eruptions Phocanaema spp. Parasite restricted to the stomach of man May try to penetrate stomach wall causing pain 39

40 Nematodes e.g. Anasakis spp. Control cook fish well Will survive : Freezing -20 o C for > 5 days Fresh water > 10 weeks Salting 21% for > 10 days In whole fish cooked at 60 o C > 5 minutes Cold smoking Pickling 40

41 Sushi or sashimi - tasty but risky If you can t resist avoid fresh water species 41

42 Fish is good for you! Good source of vitamins and minerals High quality protein Omega-3 fatty acids Reduce heart disease Essential during pregnancy May help reduce problems with Blood pressure, autoimmune, skin, kidney etc 42

43 A couple of final risks from fish They can eat you even in Europe 43

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46 Web links Schistosomiasis Filariasis Onchocerciasis Malaria Cholera 46

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48 Thank you For more information postgraduate course and lecture notes see 48

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Aquaculture and human health

Aquaculture and human health Jimmy Turnbull Institute of Aquaculture University of Stirling Scotland UK 1 Introduction zoonosis The transmission of a disease from an animal or nonhuman species to humans.